1. on sight - Noun
2. on sight - Phrase
(idiomatic) Immediately when sighted.
I recognized him on sight.
(by extension) Immediately something has come to one's attention.
He dismissed the idea on sight.
on sight (plural on sights)
(climbing) An ascent of a route without falling, when one has been advised on it or has seen it.
At a distance, we cannot conceive of the authority of a despot who knows all his subjects on sight. Stendhal
And as for Gussie Fink-Nottle, many an experienced undertaker would have been deceived by his appearance and started embalming him on sight. P. G. Wodehouse
We will shoot [any Vietnamese migrants] on sight. Mahathir bin Mohamad
Be able to identify the most common breeds of dogs and cats on sight. Marilyn vos Savant
I sent The World Well Lost to one editor who rejected it on sight, and then wrote a letter to every other editor in the field warning them against the story, and urging them to reject it on sight without reading it. Theodore Sturgeon
Being blonde means people decide on sight that you are much prettier and nicer than you really are, just as Americans automatically add 10 points to someone's IQ when they hear an English accent. Fact. Rachel Johnson